The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
A P trap is a common feature of plumbing fixtures and is essentially a device that maintains a body of water between sewer gases and the exterior of the fixture. Although they have been in use for some time, a P trap can still suffers from a number of disadvantages. For example, in the absence of an evaporation barrier liquids held within the P trap will evaporate over time. Once the water in the P trap has evaporated the plumbing fixture is able to vent unpleasant odors and dangerous gases directly from the sewage system. Typical evaporation barriers include the provision of a layer of low density, insoluble oil, however over time this oil is lost and must be replaced. Other alternatives include the use of highly flexible covers that deform readily to permit the passage of water through the fixture. Over time, however, the materials from which these valves are constructed become stiff, which can deform that valve and render it ineffective. Such covers and valves can also protrude, which limits their utility with floor drains.
In addition, P traps are not always successful in prevent pests from moving up a sewer line and exiting from a plumbing fixture. Some insect pests, notably cockroaches, are able to traverse the water barrier of a P trap and reach the associated plumbing fixture. Since such fixtures can be found in bathrooms, food preparation areas, and other areas where cleanliness is very important this is clearly undesirable. A layer of oil, such as is commonly used in conventional waterless urinals, does not prevent these pests from exiting the drain.
Some have sought to solve the problem by providing exhaustion system for a toilet. For example, U.S. Pat. No. 6,073,275 to Klopocinski discloses an odor exhaust system which withdraws gases from the toilet bowl and delivers them to the sewage drain downstream of the toilet water trap. In Klopocinski, an order extraction trap and valve is connected to the exhaust trap, and the valve is moved to an open position when the exhaust fan is operating, and the valve is closed when the exhaust valve is turned off. However, the valve movement is coupled with the operation of motorized fan, which is operated manually by the user.
Others have sought to solve the problem by providing an air vent valve that can change its position upon the air pressure. For example, U.S. Pat. No. 7,140,388 to Chalich discloses a dual ball valve air vent valve. In this system, two balls are sitting on an O-ring sealing gaskets. When the air pressure in the conduit changes, the two balls can float to provide a venting space between the balls and the sealing gaskets.
Others have sought to solve the problem by providing multiple sealing seats for a valve. For example, U.S. Pat. No. 4,796,665 to Christiany discloses a valve body with multiple sealing seats. In Christiany, a valve element changes its position between the multiple sealing seats to control flows through the valve body. However, Christiany's valve element changes positions in response to the amount of downward fluid flow, not to the upward gaseous flow from the sewage system.
All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Thus, there is still a need for a mechanism that can provide a stable, low maintenance barrier to evaporation from such traps, and also for a simple and reliable trap that can be easily added to existing fixtures.